Operating Instructions (Rev 1/99)
24
2. HEATER CONTACTOR (Optional). The heater con-
tactor is used to control the operation of the optional
electric evaporator heaters.
Other Controls
1. DEFROST TERMINATION SWITCH. This tempera-
ture sensitive switch is located on the evaporator coil.
It closes to enable defrost when the evaporator coil
temperature falls below 42 F (5.6 C).
The switch opens to terminate, or disable, defrost when
the evaporator coil temperature rises to 52 F (11.1 C).
2. CONDENSER FAN PRESSURE SWITCH. This pres-
sure sensitive switch is located on the receiver tank.
When the pressure in the receiver tank rises above 180
psi (1241 kPa), the switch closes to energized the con-
denser fan. When the pressure in the receiver tank falls
below 130 psi (896 kPa), the switch opens to de-ener-
gize the condenser fan.
3. LIQUID INJECTION SWITCH. This temperature sen-
sitive switch is located on the discharge fitting of the
truck engine compressor. When the discharge tempera-
ture rises above 230 F (110 C), the switch closes to
open the liquid injection solenoid. When the discharge
temperature falls below 200 F (93 C), the switch opens
to close the liquid injection solenoid.
4. SUCTION PRESSURE REGULATOR VALVE. This
valve is located in the suction line in the evaporator. It
limits the suction pressure at the compressor. The nor-
mal pressure setting for this valve is 18 to 20 psi (124 to
138 kPa).
UNIT PROTECTION DEVICES
1. PC BOARD FUSES. Five fuses are located on the PC
board in the low voltage box.
F1 This 15 amp fuse protects the circuit to the con-
denser fan motor.
F2 This 15 amp fuse protects the circuit to the evapo-
rator fan motor.
F3 This 10 amp fuse protects the circuit to the power
relay and the heat relay.
F4 This 3 amp fuse protects the circuit from the trans-
former output to the cab control box.
F5 Defrost Circuit Fuse. 1 Amp
F6 A 40 amp fuse protects the battery circuit.
F7 A 10 amp fuse protects transformer motor circuit
for 115V/1 Ph/60 Hz, 230V,1 Ph/60 Hz, and 230V/
1 Ph/50 Hz. A 4 amp fuse protects the transformer
motor circuit for 230V and 400V at 3 Ph, 50 units
and 230V, 3 Ph, 60 Hz units.
2. CIRCUIT BREAKER. A 40 amp circuit breaker or 40
amp fuse protects the circuit from the vehicle battery to
the unit.
3. HIGH PRESSURE CUTOUT SWITCH. This pressure
sensitive switch is located on the receiver tank. If the
pressure in the receiver tank rises above 350 psi (2413
kPa) for R-134a systems or 470 psi (3241 kPa) for R-
404A systems, the switch opens the circuit to the
power relay, which stops the unit.
NOTE: This operation is for units with printed circuit
board manufactured prior to 3-25-96 (see “P.C. Board
P/N 41-776 (First Version)” on page 38).
When the HPCO opens on models using printed ciruit
board manufactured between 3-26-96 and 5-21-96,
see “P.C. Board P/N 41-1619 (Second Version)” on
page 39 or after 5-21-96 (see “P.C. Board P/N 41-
1812 (Third Version)” on page 40) the HPCO will
cycle the compressor clutch only.
4. LOW PRESSURE CUTOUT SWITCH. This pressure
sensitive switch is located on the suction line in the
evaporator. If the pressure in the suction line falls
To Next Page
Loading...
Need help?
General
